1. Field of the Invention
The present invention relates to electronic components, and in particular, to methods and thermal assemblies for enhancing heat dissipation from electronic components.
2. Description of Related Art
Modern electronic modules include microchips and other circuit components mounted on printed circuit boards. Over the years, the speeds and power requirements of these modules have rapidly increased while the sizes thereof have shrunk. Overall, this has lead to a significant increase in power density.
During normal operating conditions, these modules generate heat or thermal energy from the microchips and other components. While some low power electronic components are able to dissipate this generated heat directly into the ambient, most require assistance to dissipate any heat that is generated during normal operating conditions.
Cooling plates or heat sinks are often used to assist high power electronic components to absorb, channel away and dissipate heat. In so doing, thermal contact is required between the heat-generating component and the cooling plate or heat sink. Since air is generally not a good thermal conductor, thermal contact is often accomplished through the use of thermally conductive materials. These materials may include, for example, thermal pastes, liquids, greases, gels, and the like. The heat sink is mechanically held to the substrate or circuit board by using bolts, adhesives, springs and the like so as to control the gap between the heat sink and the heat-generating component.
In addition to the thermal materials, retaining devices may be used, with or without the thermal materials, to maintain the thermal material between the two components. For instance, thermal pillows, o-rings, adhesives, pads, and the like, may all be used to help transfer heat between the two surfaces and/or retain the thermal material between such surfaces. However, each of these known devices brings with it the issues of stress management deficiencies, manufacturing complexity, reliability concerns and/, or high costs. Any stress management deficiencies can lead to premature device failure.
Several conventional assemblies also have rigid configurations for making the connection between the heat-generating component and the cooling plate or heat sink. However, since flexibility remains important to the mounting design to ensure constant contact while under vibration and shock induced forces, rigid configurations are often undesirable since they yield to such forces, and can potentially lead to premature device failure.
Another concern with current assemblies is that during normal operating conditions, the electronic module may undergo thermal pumping Thermal pumping occurs when the module is deformed, due to differential thermal expansions or mechanical loads, leading to extrusion of the thermal material from the gap between the cooling plate or heat sink and heat-generating component. This extruded thermal material then remains outside the gap during continued operations, leading to inefficient thermal performance, and potentially even early device failure. Little in the prior art adequately or efficiently addresses this undesirable affect of extruded thermal material during normal operating conditions.
Thus, a need continues to exist in the art for improved thermal assemblies, and methods of making such assemblies, that maximize the heat transfer rate for cooling/heating electronic modules, and in particular, those having high power flux. These methods and assemblies are preferably inexpensive, easy to assemble and/or disassemble for allowing reworkability or replacement of damaged or inoperative chips, allow for numerous electronic components to be mounted on the module or on the circuit board, and allow for flexible mounting designs to ensure constant contact between the two surfaces under vibration and shock induced forces. The methods and assemblies also provide a solution to the issue of extruded thermal material due to pumping conditions.